Fluorosulfonylimide salts are useful compounds in a wide variety of fields, and are used as electrolytes, as additives added to the electrolytes of fuel cells, and as selective electron withdrawing compounds and the like (see Patent Document 1). Fluorosulfonylimide alkali metal salts and various fluorosulfonylimide onium salts can be obtained by reactions using an alkali metal compound or an onium compound. Fluorosulfonylimide ammonium salts are useful as production intermediates for fluorosulfonylimide alkali metal salts and fluorosulfonylimide onium salts other than the ammonium salts.
Various processes have been proposed for synthesizing fluorosulfonylimide ammonium salts. For example, Non-Patent Document 1 discloses a process of synthesizing a di(fluorosulfonyl)imide ammonium salt from di(fluorosulfonyl)imide and ammonia.
Patent Document 2 discloses a process for synthesizing a bis[di(fluorosulfonyl)imide]onium salt by reacting di(chlorosulfonyl)imide with an onium compound to obtain a chlorosulfonylimide onium salt, and then reacting this onium salt with a fluoride containing at least one element selected from the group consisting of elements of group 11 to group 15 in the fourth period to sixth period (but excluding arsenic and antimony). Examples of the fluoride available in the production process described in Patent Document 2 include zinc fluoride (ZnF2), copper fluoride (CuF2) and bismuth fluoride (BiF2). These compounds are all solid substances at normal temperature.
Further, Non-Patent Documents 2 and 3 disclose a process for directly synthesizing di(fluorosulfonyl)imides from di(chlorosulfonyl)imides using arsenic trifluoride (AsF3) or antimony trifluoride (SbF3) as a fluorinating agent.